Natural and cultured populations of the mangrove oyster Saccostrea palmula from Sinaloa, Mexico, infected by Perkinsus marinus

The mangrove oyster Saccostrea palmula coexists with the pleasure oyster Crassostrea corteziensis in coastal lagoons of northwest Mexico. Recent discovery of Perkinsus marinus infecting the pleasure oyster in the region prompted evaluation of S. palmula as an alternative P. marinus host. An analysis to determine the possible presence of P. marinus in natural and cultured populations of S. palmula at four coastal lagoons in Sinaloa, Mexico was carried out during October-November 2010. Tissues from apparently healthy S. palmula were evaluated using Ray's fluid thioglycollate method (RFTM), which revealed a Perkinsus sp. to be present in all four locations at 6.7-20.0% prevalence. Histopathological analysis of these specimens showed tissue alterations and parasite forms consistent with moderate P. marinus infection, which was confirmed by ribosomal non-transcribed spacer (NTS)-based PCR assays on DNA samples from oysters positive by RFTM and histology. DNA sequencing of amplified NTS fragments (307 bp) produced a sequence 98-100% similar to GenBank-deposited sequences of the NTS from P. marinus. Fluorescent in situ hybridization for Perkinsus spp. and P. marinus corroborated the PCR results, showing clear hybridization of P. marinus in host tissues. This is the first record of P. marinus infecting a species from genus Saccostrea and the first record of the parasite from coastal lagoons in Sinaloa, Mexico.